Gas powered turbines, such as those used in commercial and military aircraft, include a compressor that compresses air, a combustor that mixes the compressed air with a fuel and ignites the mixture, and a turbine section through which the resultant combustion gasses are expanded. The expansion of the combustion gasses across the turbine section drives the turbine section to rotate. The turbine section is connected to the combustor section via one or more shafts, and the rotation of the turbine section drives the compressor section to rotate.
Multiple compressor and turbine stages are included in each of the corresponding sections, with each stage including a rotor and a corresponding stator or a corresponding vane. Rotor based systems, such as a gas turbine engine, often display coupled vibratory modes during engine operation. A coupled vibratory modes place high vibratory stresses on the rotor disk, the rotor blade, or both the rotor disk and the rotor blade when the engine is operating at or near a certain frequency.
Further, any given rotor blade or rotor disk can include multiple distinct vibratory modes, with each distinct vibratory mode corresponding to a particular engine rotational speed. In an ideal engine, every vibratory mode of a given rotor assembly is tuned to fall significantly higher than the frequency range of the typical engine operation. However, tuning rotor disks and rotor blades such that the vibratory modes fall significantly higher than the frequency range of typical engine operation significantly increases the weight of the corresponding rotor, and is not practical in all cases due to engine component size constraints.